Power control of a multi-cell solid-state transformer with extended functions

Electric energy is usually generated through power stations (hydroelectric, gas, coil, nuclear) interconnected to ensure the power supply; but in the last years a massive number of renewable energy resources have been integrated in the electric grid helping to fulfill the power demand. Nevertheless, the interconnection of multiple generation along the distribution system affects the power quality in medium and low voltage grids (MVAC, LVAC respectively). A solution for this is the incorporation of power quality compensators to the MVAC-LVAC coupling transformers; known as Solid-State Transformer (SST) substituting the conventional transformer and adding power quality compensation features. This paper presents a modular multilevel converter based on SST for the coupling of a low voltage grid (127 V rms ) to a medium voltage distribution system at 3.6 kV, with harmonic filtering capabilities.